This time of year, weight loss—and weight gain—is on the minds of many. It can be fairly easy to figure out why we put on those extra pounds during the holidays. After all, it’s that time of the year when our eating habits slip a bit and we may indulge in more sweets, other fattening foods and alcohol. But there are also other reasons why we gain weight that may surprise you. Let’s start with sleep.

Sleep is serious business
Several recent studies have linked lack of sleep (less than six hours a night) to increased risk of obesity. A 2011 study featured in the journal Clinical Endocrinology & Metabolism demonstrated that even just one night of sleeping four or fewer hours can put your body into a state of insulin resistance, which is associated with increased obesity.

“When we are sleep deprived, we disrupt the daily circadian rhythm that controls blood sugar balance, and we can lose insulin sensitivity, causing us to gain weight,” explains Lise Alschuler, ND, coauthor of Five to Thrive: Your Cutting-Edge Cancer Prevention Plan (Active Interest Media, 2011). “Our bodies are simply not programmed to manage our blood sugar levels on insufficient sleep.”

If you’re trying to lose weight, you may want to take a closer look at your sleep habits. Alschuler says most people need seven to nine hours of shut-eye for overall wellness and to help prevent insulin resistance.

Portion control
Perhaps portion control seems a bit obvious; however, the perception of a “normal” portion size has expanded right along with our waistbands. Some of the most interesting research in this area has been done by Barbara J. Rolls, PhD, of Penn State University.

In several studies, Rolls and her colleagues have shown that portion size directly dictates how much study participants eat. Whether it’s macaroni and cheese, potato chips or popcorn at a movie theater, her research shows that if people are given a larger portion, they consistently eat the entire portion, while those given a smaller portion consistently eat less.

Changing your perception of portion size may not be easy. For example, the “normal” amount of meat protein needed at a meal is 3 to 4 ounces, or the size of a deck of cards. Can you image ordering a steak at a restaurant and getting a 3-ounce portion? What’s the solution? Being mindful of portions at mealtime and using these tips from Alschuler will help you reduce your portion size:

• At mealtime, consistently take 25 percent less food than what you think you want; you won’t miss it, and you will slowly train yourself to want less with each meal.

• Use smaller plates and bowls.

•  Eat slowly, and put down your utensils between bites.

• When eating out, suggest splitting an entrée with a dining companion or ask about smaller portions or half plates.

• Drink water before your meal and take some extra sips of water between bites of food.

• Eat smaller meals throughout the day rather than waiting until you are excessively hungry; this will help prevent binging on big meals.

• Don’t eat while watching TV, as this will distract you and cause you to eat more.

Of course, it’s impossible to talk about losing weight without a few comments on exercise.

Preventing that plateau
When it comes to weight loss, there is nothing more frustrating than putting on weight while you are working out. One reason you may stop losing or, even worse, start gaining weight when you’re exercising consistently is that you’ve hit a workout wall. That’s the wall you run into after you’ve been doing the same fitness routine for a long period of time. According to sports medicine expert Susan Ryan, DO, the human body will actually adjust to your exercise routine and get used to it. It’s your body’s way of being efficient, but it can drive you crazy if you’re trying to lose weight.

Ryan says one of the best ways to push through plateaus is by switching up your routine with pops of intensity. For example, if you are used to walking around the neighborhood for 30 minutes after work, try bursts of jogging or running for a block, or speed up the pace for a few minutes every five minutes of your route. Also, add some strength-training exercises and stretches to your workout. If you’re a more seasoned exerciser, you may want to intersperse an entirely new type of exercise into your routine. Try Pilates, yoga or NIA (a combination of modern dance and martial arts movements).

Preventing or even busting through an exercise plateau will help you overcome a weight-loss standstill and also help you lose those extra pounds you put on over the holidays.

Get creative, but most of all, says Ryan, think of these changes as a way of life, not just temporary weight-loss strategies.